A special investigation team set up in Pakistan to probe a deadly assault on an Indian air base last month found no evidence implicating the leader of the group India blamed for the attack, Pakistani security officials said on Monday. The officials said the team interrogated Jaish-e-Mohammad chief Maulana Masood Azhar and his associates and found no evidence linking him with the Jan. 2 attack on the Pathankot air base in northern India that killed seven Indian military personnel. "We searched their homes, seminaries, hideouts and also examined their call records for past three months and found nothing dubious," a security official with links to the investigating team said. The raid on the air base stalled efforts to revive bilateral talks between the nuclear-armed neighbours after Indian Prime Minister Narendra Modi made an unscheduled visit to his Pakistani counterpart, Nawaz Sharif, in December. The security officials said on Monday that Azhar remained in custody, but did not say whether authorities were considering his release. The investigating team has not ruled out the possibility that other members of Azhar's group may have been involved, the officials said. It also continued to look into groups affiliated with the United Jihad Council, an alliance of pro-Pakistan militant groups based in the Pakistani-administered part of the divided Kashmir region that claimed responsibility for the assault in Pathankot. Jaish-e-Mohammad did not claim responsibility for the attack, but praised it in a statement released a few days afterward.